1. Field of the Invention
The present invention generally relates to communication devices installed in communication stations and plug-in units therefor, and more particularly to a communication device having reduced EMI (electromagnetic interference) that is an electromagnetic interference noise generated from the device, reinforced resistance to static electrical discharge, increased flame resistance, and increased efficiency of forced air-cooling.
The importance of communication in recent years requires an improvement in the quality of communication devices installed in communication stations. In terms of quality, the communication devices are required to keep EMI emitted therefrom sufficiently low. For instance, the communication devices are required to satisfy the FCC. part 18 standard employed in North America.
2. Description of the Related Art
A common communication device includes a plurality of plug-in units mounted side by side in a sub-rack attached to a rack.
Conventionally, EMI has been coped with by covering the front side of a sub-rack having plug-in units plugged thereinto. Although this provides a shield that collectively shuts off the electromagnetic interference noises radiated from the respective plug-in units, this may not be sufficient as a measure against the EMI.
It is a general object of the present invention to provide a communication device and a plug-in unit therefor in which the above-described disadvantage is eliminated.
A more specific object of the present invention is to provide a communication device and a plug-in unit therefor that provide a shield against electromagnetic interference noises of higher frequencies.
The above objects of the present invention are achieved by a communication device including: a sub-rack unit including a back wiring board having first connectors arranged in lines thereon, and a frame plate including vertical ribs and placed on the back wiring board so that the vertical ribs separate the lines of the first connectors; and a plurality of plug-in units each including a printed board including top and bottom sides and parallel first and second sides perpendicular to the top and bottom sides, the printed board having second connectors provided on the first side thereof, a metal case including top and bottom faces and parallel first and second side faces perpendicular to the top and bottom faces so as to cover the printed board, and first and second spring members, wherein each of said plug-in units is mounted in the sub-rack unit with the first and second connectors being connected so that the first and second side faces of the metal case are pressed outward against the vertical ribs of the frame plate by resilient forces generated by elastic deformation of the first and second spring members, respectively.
This communication device provides a shield against an electromagnetic interference wave of a frequency as high as 10 GHz. Without the first and second spring members, the metal case is pressed against the vertical ribs by resilient forces of their own, which may cause an imperfect contact of the metal case with the vertical ribs. In this case, a shield effect is limited to electromagnetic waves of lower frequencies, and is not produced on an electromagnetic wave of a frequency as high as approximately 10 GHz. According to this communication device, the resilient forces of the spring members press, against the vertical ribs of the frame plate, the edge of an opening formed on an end of the metal case in a direction in which each plug-in unit is inserted into the sub-rack unit. Therefore, the edge of the opening securely contacts the vertical ribs of the frame plate. This provides a shield against, for instance, an electromagnetic interference noise of a frequency as high as 10 GHz, not to mention electromagnetic interference noises of lower frequencies.
Therefore, a shield is provided against electromagnetic interference noises of high frequencies as well as those of low frequencies that leak out from each plug-in unit mounted in the sub-rack unit.
The above objects of the present invention are also achieved by a plug-in unit to be mounted in a sub-rack unit including connectors, which plug-in unit includes: a printed board including connectors provided on a side thereof, the connectors being connected with the connectors of the sub-rack unit so that the plug-in unit is mounted therein; a metal case including top and bottom faces, and parallel first and second side faces perpendicular to the top and bottom faces so as to cover the printed board; and first and second spring members elastically pressing outward the first and second side faces of the metal case, respectively.
This plug-in unit has the same effect as the above-described communication device by providing a reliable contact of the metal case with the sub-rack unit when the plug-in unit is mounted therein.
The above objects of the present invention are also achieved by a plug-in unit to be mounted in a sub-rack unit including connectors, which plug-in unit includes: a printed board including parallel first and second sides and having connectors provided on the first side thereof, the connectors being connected with the connectors of the sub-rack unit so that the plug-in unit is mounted therein; a photoelectric conversion module provided on the printed board; a front member attached to the second side of the printed board, the front member having a space formed therein; and a rotating member holding adapters for connecting optical connectors, the rotating member being supported in the space of the front member so as to be rotationally moved between a position in which the rotating member is housed in the space with the adapters facing downward and a position in which the adapters protrude from the front member through an opening formed on a first side thereof to face slantingly downward, the first side facing a reverse direction to said printed board, wherein plugs provided on ends of optical fibers extending from the photoelectric module are connected to the adapters.
According to this plug-in unit, the eyes of a user are protected from laser beams when the user connects the plugs of the optical fibers with the adapters. Further, this plug-in unit is allowed to have a larger number of adapters than a conventional plug-in unit.
The above objects of the present invention are also achieved by a communication device including: a sub-rack unit including a back wiring board having connectors, and first and second guide rail parts being attached to a top side and a lower portion of the sub-rack unit, respectively; a plurality of plug-in units being inserted along the first and second guide rail parts into the sub-rack unit to be plugged into the connectors of the sub-rack unit; a member for forming an air reservoir room formed under the second guide rail parts; and a plurality of motor-fan units each having a motor fan, the motor-fan units being plugged into the sub-rack unit under the member for forming the air reservoir room.
According to this communication device, air from the plugged motor-fan units enters the air reservoir room first and then the sub-rack unit. By this structure, the air equally blows up inside all the mounted plug-in units so that all the plug-in units are forcibly air-cooled equally.
The above objects of the present invention are further achieved by a plug-in unit to be mounted in a sub-rack unit, which plug-in unit includes: a front member including a convex part; and first and second card lever assemblies attached to top and bottom end portions of the front member, respectively, each of the first and second card lever assemblies including a main body and an auxiliary lever having a hook part and supported by the main body so as to be rotationally moved around a rotation center, the hook part being formed on an elastically deformable frame part having a frame shape with a hole formed therein, wherein the hook part of the auxiliary lever is positioned on a level with the rotation center in a direction in which the plug-in unit is inserted into the sub-rack unit when the hook part engages with the convex part of the front member.
According to this plug-in unit, the hook part is not disengaged from the convex part even if a force to dismount the plug-in unit from the sub-rack unit is exerted. Therefore, the plug-in unit is mounted in the sub-rack unit in a locked state with high reliability.